MITOCHONDRIAL-DNA SEQUENCE DIVERGENCE IN WEEVILS OF THE PISSODES STROBI SPECIES COMPLEX (COLEOPTERA, CURCULIONIDAE)

Mitochondrial DNA sequence divergence is unusually high between severa l species of the Pissodes strobi complex, in contrast to low allozyme and morphological divergences, and the ability to hybridize in the lab oratory. We sequenced an 810 bp segment in seven individuals, represen ting four species in the P. strobi complex and one outgroup species, P . affinis Randall. The 810 bp segment covered the 3' half of the cytoc hrome oxidase subunit I (COI) gene. We also sequenced one specimen of P. strobi (Peck) over a 2301 bp region of mtDNA, extending from the 5' end of COI to the 3' end of COII. Uncorrected sequence divergences we re below 1.1% among three specimens of P. schwarzi Hopkins, and betwee n P. terminalis Hopping and P. nemorensis Germar. All other interspeci fic combinations in the P. strobi complex showed divergences of 6.0-7. 5%. The outgroup species, P. affinis, had an average divergence of 12. 8% from members of the P. strobi group. As in most other insects, A+T content in Pissodes mtDNA was high; transition:transversion ratio was high among lineages exhibiting low divergences, but declined with incr easing sequence divergence; and inferred amino acid sequence divergenc es were low. The degree of sequence divergence differs markedly across different functional regions of the COI gene. The high mtDNA divergen ces within the P. strobi complex calculated from direct sequencing sup port earlier reports based on restriction site surveys; however, clado grams based on mtDNA sequence differ from those based on earlier work.